When carrying out foundation and soil consolidation drilling, soil drilling machines are used, which usually are self-moving.
The aforesaid type of machines typically has a self-moving structure provided with a frame on support wheels or tracks, lifting winches for drilling accessories, and a rotary turret on a fifth wheel coupled to the support tracks and comprising a cabin as well as control accessories. The rotary turret is usually provided with a power assembly, for example a heat engine or an electric motor, for the cabin, for the control accessories and, typically, for the lifting winches.
This type of machine usually comprises a mast provided with sliding guides where a rotary slides linearly translates, said rotary being associated with the drilling accessories of the machine, for example a drill string or a drilling tool. The rotary, in particular, receives power, for example hydraulic power or electric power, from the power assembly and turns it into a rotary movement adapted to move the drilling tools.
The mast is commonly delimited, at the top, by a head comprising a plurality of pulleys for one or more ropes, through which the lifting winches located on the turret lift or lower the drilling accessories. The latter usually are unconstrained in an axial direction, but not in a radial direction, relative to the rotary, which is provided with an independent lifting/lowering system.
In case large drilling depths are requested, the typically used technical solution is that of applying the drilling tools to a telescopic drill string containing telescopic kelly rods. More in detail, said drill string usually comprises a plurality of kelly rods having a decreasing cross-section and capable of axially sliding inside one another. These kelly rods are structured so as to transmit the rotary motion and the pushing forces, needed to move forward, to one another. When they are installed in the machine, said kelly rods cross the rotary.
Strings of telescopic kelly rods are usually divided into two types: friction kelly rods and mechanical locking kelly rods.
In friction kelly rods, the torque is usually transmitted between the kelly rods by means of engaging organs, for example longitudinal strips welded along the elements making up the kelly rod, both on the inside and on the outside, so that they can engage one another. Therefore, the transmission of the axial thrust between the kelly rods takes place by means of the friction between the strips generated in the presence of torque.
The rotary, then, has a coupling sleeve which is also provided with engaging means, such as a plurality of inner strips adapted to engage corresponding outer strips of the most external kelly rod of the drill string. In this way, the most external kelly rod of the drill string receives the rotary motion from the rotary through the engagement between the strips of the sleeve and the outer strips of the kelly rod, whereas the transmission of the axial thrust takes place through the friction between the strips of the sleeve and the ones of the most external kelly rod, which is generated in the presence of applied torque. In the absence of applied torque, the kelly rods can axially slide relative to one another and the entire drill string can slide relative to the rotary and is moved by a proper flexible element, preferably a cable.
A drawback arising from the use of friction kelly rods lies in the fact that the transmission of thrust from a kelly rod to the other exclusively takes place through the friction between engaging means, such as strips; therefore, the applicable thrust is only the one allowed by the friction that can be generated.
If the thrust limit value is exceeded, the friction is not sufficient any longer and there is a mutual axial sliding between the kelly rods, so that this thrust cannot be unloaded onto the drilling tool.
Also due to the drawback described above, when drilling operations must be carried out in soils having hard layers, rocks or pebble, it is preferable to use strings of mechanical locking telescopic kelly rods.
An example of mechanical locking kelly rods will now be described with reference to FIGS. 1A and 1B and with reference to the soil drilling machine where these kelly rods can be installed, which is shown in FIGS. 2A and 2B.
FIGS. 2A and 2B show, in particular, a drill string 20 comprising plurality of telescopic kelly rods 20A, 20B, 20C.
More specifically, FIG. 1A shows a first kelly rod 20A (outer kelly rod), which has the greatest diameter in the entire drill string 20 to which said kelly rod belongs. FIG. 1B, on the other hand, shows the last kelly rod 20C (inner kelly rod), which has the smallest diameter in the entire drill string 20 to which said kelly rod belongs.
According to FIGS. 2A and 2B, drill string 20 further comprises an intermediate kelly rod 20B, which can telescopically slide inside outer kelly rod 20A and in which, in turn, the intermediate kelly rod 20C can telescopically slide. In any case, the drill string can comprise any number of further intermediate kelly rods arranged inside one another.
Anyway, the number of kelly rods can range from a minimum of two (hence, the sole outer kelly rod 20A and inner kelly rod 20C, which, in this case, can slide relative to one another without the interposition of one or more intermediate kelly rods 20B) to a maximum number which depends on the diameter of the outer kelly rod 20A, but—in the prior art—usually is not greater than ten.
With reference to the mechanical locking kelly rod 20A of FIG. 1A, on the outer surface of the tubular body of the kelly rod there are longitudinal strips 21A, which extend over the entire length of the body. These strips 21A can be multiple and equally spaced apart from one another along the outer circumference of the kelly rod, in a number depending on the diameter of the kelly rod. Each strip 21A has, in the area of the top of the kelly rod, an engagement portion, for example an upper recess 22A, and has, in an intermediate portion of its length, a further engagement portion, for example an intermediate recess 23A. In any case, each strip can also have further engagement portions (for example recesses that are similar to the ones described above), which are obtained on it in different axial positions. Alternatively, each strip can also have one single engagement portion (such as a recess that is similar to the ones described above). Clearly, the engagement portions can also be located on the outer kelly rod 20A in positions that are different from the ones described and disclosed herein.
The aforesaid recesses 22A, 23A make up seats with a substantially rectangular shape where interlocking portions can be engaged, for example the strips (not shown) of the sleeve of rotary 10, thus remaining axially locked therein. By so doing, the strips of the sleeve of rotary 10 can transmit to kelly rod 20A both the torque, by means of a contact of the side of the strips of the sleeve with strips 21A, and the thrust, by means of a mechanical abutment striking between the base of the strips of the sleeve and the pushing surface in the lower part of recesses 22A. When the inner strips of the sleeve of rotary 10 are engaged in the seats created by recesses 22A of the outer kelly rod 20A, the latter is axially constrained to rotary 10. Through a rotation of the sleeve of the rotary in an opposite direction, on the other hand, the strips of the sleeve of rotary 10 can be disengaged from the seats created by recesses 22A of the outer kelly rod 20A, thus allowing kelly rod 22A to slide relative to the rotary.
At the upper end of the outer kelly rod 20A there is an upper abutment flange 24A, which has a greater diameter than the tubular body of the outer kelly rod 20A and acts as a limit stop, thus stopping the sliding of the outer kelly rod 20A relative to the sleeve in which the outer kelly rod 20A is inserted. For the transmission of torque and thrust between the outer kelly rod 20A and the intermediate kelly rod 20B, the principle basically is the same: at the lower end of the outer kelly rod 20A there is a sleeve 25A with interlocking portions, for example projections, in particular strips 26A facing inwards, which can be coupled to complementary engagement portions 22B, 23B of the intermediate kelly rod 20B. These strips 26A usually have a length that is much smaller than the one of the outer kelly rod 20A and, in particular, they have a length that is slightly smaller than the one of engagement portions, for example recesses where they can be engaged, and, therefore, they are adapted to be engaged in recesses of the second kelly rod 20B.
The intermediate kelly rod 20B and the inner kelly rod 20C making up drill string 20 all have a geometry that is substantially similar to the one of the outer kelly rod 20A and, therefore, these features will not be described in detail and reference is made to the description above. In particular, the intermediate kelly rod 20B and the inner kelly rod 20C also have outer longitudinal strips 21B, 21C, an upper abutment flange 24B, 24C, engagement portions (for example, an upper recess 22B and an intermediate recess 23B located on the intermediate kelly rod 20B and, respectively, an upper recess 22C and an intermediate recess 23C located on the inner kelly rod 20C), lower sleeves 25B, 25C provided with respective interlocking portions (for example, the inner strips 26B, 26C) complementary to the engagement portions.
Unlike the other kelly rods 20A, 20B of drill string 20, the inner kelly rod 20C (namely, the most internal one) is advantageously provided with a recovery flange 27C, which is constrained to the lower part of the body of the kelly rod. All the most external kelly rods 20A, 20B rest on the recovery flange 27C when they are in an unlocked condition, namely when they are axially unconstrained. At the top of the inner kelly rod there is an upper hooking terminal 28C for a kelly rod supporting and moving rope, which is connected, for example, through the interposition of a rotary joint. At the lower end of the inner kelly rod 20C there is a connection terminal, which allows a drilling tool 15 to be connected to the kelly rod 20C.
As already mentioned above, the known soil drilling machine 100 uses a drill string 20 of mechanical locking kelly rods described above.
Machine 100 is provided with a kinematic mechanism 2, preferably shaped like a parallelogram, for moving a mast 5 relative to a turret 3, which is mounted in a rotary manner on a self-moving carriage 4. Turret 3 comprises a control cabin for the operator. The operation of kinematic mechanism 2 allows mast to be moved both in order to adjust the drilling height relative to the center of the fifth wheel and in order to adjust the inclination relative to the ground level. These movements are also made possible by an articulated joint 6, such as a universal joint, interposed between mast 5 and kinematic mechanism 2. On mast 5 there is located a rotary 10, which is provided with a known pulling-pushing system 11. A telescopic drill string 20 is arranged through rotary 10 so as to receive torque and thrust from rotary 10.
Telescopic drill string 20 is guided, in the lower part, by the sleeve of rotary 10 and, preferably also in the upper part, by a rod-guiding head 13. A drilling tool 15, which can consist, for example, of a bucket or helical drill, is fixed to the lower end of the inner kelly rod 20C of drill string 20, so that it can receive torque and thrust from said inner kelly rod 20C.
Telescopic drill string 20 is moved by means of a winch 8, also known as main winch, which is supported by turret 3 of machine 100 and is configured to permit the winding or unwinding of a pulling element 9, for example a rope, which is fixed to winch 8 and, after having been turned on head 7 of the mast, is constrained to the most internal kelly rod of drill string 20. In particular, the connection between rope 9 and the inner kelly rod 20C takes place through the interposition of a known rotary joint 14. Rotary joint 14 fulfills the function of forbidding the transmission of torque between the inner kelly rod 20C and rope 9 of winch 8, thus preventing the rope from being dragged in rotation by the rotary motion of kelly rods 20A, 20B and 20C, hence allowing the rope not to twist.
FIG. 2A shows machine 100 in a condition in which it is in position in the drilling spot with drill string 20 in a completely retracted condition, namely with the minimum length and completely lifted relative to rotary 10. In this condition, the entire drill string 20 hangs on rope 9 and is axially unconstrained relative to rotary 10. In particular, the most internal inner kelly rod 20C is constrained to rope 9 and hangs from said rope, whereas the other kelly rods 20A, 20B rest, due to gravity, on the rod recovery flange 27C, which is located at the lower end of inner kelly rod 20C.
Rod recovery flange 27C is integral to the inner kelly rod 20C and has a diameter that is at least equal to the diameter of the outer kelly rod 20A, so that all remaining kelly rods 20A and 20B of drill string 20 rest on the flange, without being capable of sliding downward.
Said plurality of kelly rods 20A, 20B, 20C is divided into a plurality of kelly rods sliding adjacent to one another, in particular:                a first pair of telescopic kelly rods, which can axially slide inside one another; in this case, said first pair consists of the outer kelly rod 20A and the second kelly rod 20B, and        a second pair of telescopic kelly rods, which can axially slide inside one another; in this case, said second pair consists of the second kelly rod 20B and the third kelly rod 20C.        
In the condition of FIG. 2A, each kelly rod 20A, 20B has its own interlocking portions, for example arranged on the respective lower sleeve 25A, 25B, which are coupled to the engagement portions of the kelly rod sliding next to it, hence the one arranged immediately on the inside, for example on the respective outer strips 21B, 21C.
Therefore, all kelly rods 20A, 20B, 20C are in a coupled condition and can transmit torque to one another. In order to start drilling, starting from the condition of FIG. 2A, drill string 20 is moved downward by unwinding rope 9 through the activation of winch 8. During this downward movement, drill string 20 axially slides inside the sleeve of rotary 10, until drilling tool 15 rests on the ground.
At this point, by operating the motors of rotary 10, a rotation can be applied to drill string 20 with a desired rotation speed and a desired torque, in a predetermined drilling direction, so that drilling tool 15 starts drilling the soil moving downward thanks to the weight of kelly rods 20A, 20B, 20C weighing upon it, which can slide relative to rotary 10. In case a further thrust needs to be applied to the drilling tool, the operator can have rotary 10 to slide along mast 5, so that rotary 10 also slides relative to drill string 20, which will rest on the bottom of the drilling site, until rotary 10 reaches a recess 23A in an intermediate position of the outer kelly rod 20A.
In this situation, by applying a rotation to the sleeve of rotary 10 in the drilling direction, the interlocking portions of the sleeve of rotary 10 engage intermediate recess 23A of the outer kelly rod.
Subsequently, by moving rotary 10 downward by means of pulling-pushing system 11, the strips of the sleeve of rotary 10 strike against the corresponding pushing surface of recess 23A of the outer kelly rod 20A. By so doing, a thrust is transmitted from rotary 10 to kelly rods 20A, 20B, 20C and to drilling tool 15 and, in this condition, drill string 20 slides downward in an integral manner with the sliding movement of rotary 10.
The aforesaid coupling of the interlocking portions or strips of the sleeve of rotary 10 to the engagement portions or recesses 23A of the outer kelly rod 20A is fairly simple to be obtained by the operator, as at least recesses 23A of the outer kelly rod are exposed and are visible from the controlling position.
When the movement of rotary 10 has caused drill string 20 to move forward to an extent that is sufficient to fill drilling tool 15, the sleeve of rotary 10 needs to be rotated in an opposite direction relative to the drilling direction, keeping tool 15 resting on the ground of the drilling site. In this way, the sleeve of rotary 10 is caused rotate relative to kelly rods 20A, 20B, 20C and the strips of the sleeve disengage recess 23A of the outer kelly rod 20A. Besides axially unconstraining kelly rods 20A, 20B, 20C relative to rotary 10, at the same time, kelly rods 20A, 20B, 20C are brought to a decoupled condition relative to one another, in which they are axially unconstrained from one another and are not capable of transmitting a thrust downward to drilling tool 15.
When winch 8 is subsequently activated, rope 9 is rewound so as to cause the kelly rods to be lifted, dragged by rod recovery flange 27C of the inner kelly rod, until tool 15 gets out of the drilling site, thus allowing the soil enclosed in the tool to be discharged.
Once tool 15 has been discharged, it is moved again to the bottom of the drilling site and the operations described above are repeated in order to apply a new thrust to the tool. When rotary 10 reaches the lower limit stop position along mast 5, no thrust can be applied any longer to drill string 20 by pressing intermediate recess 23A. Therefore, the operator will have to disengage the strips of the sleeve of rotary 10 from the intermediate recess 23A of the outer kelly rod 20A and have rotary 10 slide upward. At the same time, kelly rods 20A, 20B, 20C remain still, resting on the bottom of the drilling site, until rotary 10 reaches the upper recess 22A of the outer kelly rod 20A. In this condition, the upper flange 24A of the outer kelly rod 20A, which has a larger diameter than the kelly rod, strikes against a suitable abutment portion of rotary 10.
By applying a rotation of the sleeve of rotary 10 in the drilling direction, the strips of the sleeve of rotary 10 engage the upper recess 22A of the outer kelly rod. At this point, by moving rotary 10 downward by means of pulling-pushing system 11, the strips of the sleeve of rotary 10 strike against the corresponding pushing surface of recess 22A of the outer kelly rod 20A. By so doing, a thrust is transmitted from rotary 10 to kelly rods 20A, 20B, 20C and, in this condition, drill string 20 slides downward in an integral manner with the sliding movement of rotary 10.
Then, all the tool drilling and discharging operations described above can be repeated.
Moving on with the drilling procedure, when the depth reached is greater than the length of the outer kelly rod 20A, the condition shown in FIG. 2B occurs.
In particular, in FIG. 2B, the outer kelly rod 20A is in the lowest position relative to rotary 10, as the outer kelly rod 20A has crossed rotary 10, reaching the lower limit stop position, which means that the upper flange 24A of the outer kelly rod 20A strikes against the abutment surface of rotary 10. Hence, the outer kelly rod 20A does not hang any longer from rope 9, but now all its weight is directly borne by rotary 10, which means that it is supported by pulling-pushing system 11 of rotary 10. Therefore, in this case, drill string 20 is only partly supported (outer kelly rod 20a) by rotary 10.
The inner strips of the sleeve of rotary 10 are then in the area of the upper recesses 22A of the outer kelly rod 20A and they keep this position as long as the outer kelly rod 20A is completely lowered. Hence, the outer kelly rod 20A has reached the completely lowered position relative to rotary 10. In this situation, the strips of all kelly rods 20A, 20B, 20C are disengaged from the respective recesses by means of rotation of the sleeve of rotary 10 in a direction that is opposite to the drilling direction. Furthermore, if rope 9 is further unwound from winch 8, the outer kelly rod 20A remains still relative to rotary 10, as it is supported by rotary 10 itself. On the other hand, if rope 9 is unwound, the intermediate kelly rod 20B and the inner kelly rod 20C keep moving downward sliding relative to rotary 10 and relative to the outer kelly rod 20A. The intermediate kelly rod 20B and the inner kelly rod 20C are supported by recovery flange 27C, which, in turn, is supported by rope 9, as it is arranged on the inner kelly rod 20C.
According to FIG. 1B, when tool 15 reaches the bottom of the drilling site, it can happen that the intermediate kelly rod 20B partially slides out of the outer kelly rod 20A. In this situation, the lower sleeve 25A and its inner strips 26A are in an intermediate position between the upper recess 22B and an intermediate recess 23B. In this situation, if the operator of the machine wants to apply a thrust to tool 15, he/she needs to make rotary 10 and the outer kelly rod 20A integral thereto slide until they reach one of the two possible mechanical locking positions, in which the lower sleeve 25A and its inner strips 26A of the outer kelly rod 20A are aligned in the area either of the intermediate recess 23B or of the upper recess 22B (not shown) of the second kelly rod 20B.
Once one of these mechanical locking positions is reached, by applying a rotation in the drilling direction to the sleeve of rotary 10, the strips of the sleeve of the rotary engage the upper recess 22A of the outer kelly rod 20A and, simultaneously, the inner strips 26A of the outer kelly rod 20A engage one of recesses 22B or 23B of the intermediate kelly rod 20B. In this condition, a downward thrust of rotary 10 is transmitted both to the outer kelly rod 20A and to the intermediate kelly rod 20B by means of the interlocking of the strips in the respective recesses, then the second kelly rod 20B, by resting on the rod recovery flange 27C of the inner kelly rod 20C can transmit the thrust to the inner kelly rod 20C and to tool 15.
However, this type of soil drilling machine is affected by some drawbacks.
With reference, again, to the drilling condition shown in FIG. 2B, the moving maneuver of rotary 10 and of the outer kelly rod 20A integral thereto, until the lower sleeve 25A and its inner strips 26A of the outer kelly rod 20A are aligned in the area either of the intermediate recess 23B or of the upper recess 22B (not shown in the figure) of the second kelly rod 20B, is fairly complicated for the operator of machine 100.
The complexity of the maneuver is mainly due to the fact that both sleeve 25A and recesses 23B and 22B are not visible to the operator sitting in the cabin, as they are inside the drilling site. In order to make this maneuver, expert operators, at first, apply to drill string 20 a small torque in the drilling direction, which is much smaller than the maximum one that can be generated by the rotary and is sufficient to cause inner strips 26A of sleeve 25A to strike against the longitudinal outer strips 21B of the intermediate kelly rod 20B. After that, the operator, always keeping a small torque applied, operates pulling-pushing system 11, causing rotary 10 and outer kelly rod 20A to slide upward or downward, so that inner strips 26A of the outer kelly rod get close either to upper recess 22B or to intermediate recess 23B of intermediate kelly rod 20B. Inner strips 26A, which, at first, rest with their entire length on outer strips 21B, by sliding will end up having only part of their length in contact with strips 21B, as the remaining part overlaps a recess 22B or 23B. This contact part gets smaller and smeller, increasing the specific pressure in said contact part of the inner strip. If the applied torque is small, this pressure remains within limits allowed by the material of the strips and does not cause damages. When the sliding of outer kelly rod 20A is sufficient to cause strips 26A to completely face one of the recesses of the second kelly rod, these strips get into the recesses and are coupled to them. An expert operator is capable of perceiving when the inner strips get into the recesses, usually because of the rotation, the vibrations or the noise generated by them. Once he/she has perceived the engagement of the strips in the recesses, the operator goes on applying a greater torque to the kelly rods and also applying a thrust to the kelly rods. All the maneuvers described above must be repeated once the depth of the drilling exceeds the length of the first two kelly rods 20A and 20B and, hence, the first two kelly rods are moved in an integral manner with rotary 10 in order to try and find the interlocking positions on the following kelly rod 20C.
Therefore, a drawback of this technology lies in the fact that the detection of the correct mutual interlocking of the strips and the correctness of the sequence of maneuvers necessary for this interlocking only depend on the experience of the operator. A scarcely expert operator, starting from the condition of FIG. 2B, could choose to apply, from the very beginning, the maximum torque of the rotary while he/she makes both rotary 10 and outer kelly rod 20A slide in the search for a correspondence with the recesses of the second kelly rod 20B. As already mentioned above, during this maneuver the inner strips end up in a partial contact condition and, if the applied torque is too high, specific contact pressures can exceed the admissible limits, thus generating plastic deformations of the strips and wear of the corners of the recesses, which are so rounded, causing an excessive wear of the kelly rods and leading to a loss of efficiency of the locking system, which can make the mutual interlocking of the kelly rods impossible or not very safe. Furthermore, the problem of having to correctly aligning the kelly rods, so that the strips end up in the area of the recesses, can arise again with every tool loading and discharging cycle. As a matter of fact, assuming to start from a condition in which the inner strips of a kelly rod are coupled to the intermediate recesses of the following kelly rod, once tool 15 has been pushed until it has reached its filling, the tool has to be removed from the drilling site by winding rope 9 on winch 8, moving the entire drill string back to the minimum length contracted condition, in order to then empty the tool on the outside of the drilling site and subsequently lower again the tool up to the bottom of the drilling site by unwinding rope and extending the kelly rods. If, during the tool lifting, discharging and lowering phases, the operator has never had rotary 10 slid relative to mast 6, then the kelly rods are still correctly aligned so as to allow the inner strips and the intermediate pockets to be interlocked. If, on the other hand, the operator has moved rotary 10, leaving it in a position different from the one it had at the end of the previous drilling cycle, there is a misalignment between all the kelly rods that have completely slid out, which will be moved in an integral manner with rotary 10 relative to the bottom of the drilling site, and the kelly rods that have partially slid out, which will rest again on the bottom of the drilling site keeping the previous position. This misalignment means that the kelly rods are not any longer in the correct mutual axial condition permitting their interlocking and, therefore, the operator has to try and find, again, the position of the recesses that enables the insertion of the inner strips.
It is evident that these maneuvers require downtimes, which reduce the productivity of the drilling process. The search for the correct position of the kelly rods relative to the recesses becomes particularly complicated when pulling-pushing system 11 is of the type having a winch, as, in this solution, it is not possible to use fixed reference positions of rotary 10, which, in case of a pulling-pushing system with a cylinder, could be the top and bottom limit stop positions of the moving cylinder of rotary 10.